What are the differences between _weak_ references and "normal" references?

[Ben Hutchings]

In article <169a7283.0304040901.4bc3531b at posting.google.com>,
sdieselil wrote:
> Hi
> 
> I noticed a module weakref in Python standard library. What is weak
> reference and in what way it differs from "normal" reference? By the
> way, how can I implement usual reference in Python (I mean C++
> reference)?

All Python variables are references, but unlike C++ references they can
be rebound.  In Python, copying objects is unusual.

In a garbage-collected environment like Python, a weak reference is one
that does not prevent its target from being destroyed, but is instead
nullified (in Python, set to None) when the target is destroyed.